The present invention relates generally to shift linkage for an outboard motor, and more particularly, to a linkage assembly having a slot operably engaged with a guide to facilitate the shifting of gears during operation of the outboard motor.
Manual shift vehicles typically employ a clutch to facilitate shifting for engagement and disengagement of the gears in a standard shift transmission. However, in certain types of engine applications, such as marine outboard engines, there is no clutch system and gear shifting can occasionally demand more effort from an operator to shift from a positive gear position to a neutral position.
A typical outboard marine engine has three gearshift positions to provide operation, namely, forward, neutral, and reverse. When attempting to perform a gear shift from forward to neutral, or reverse to neutral, additional effort can be required for a number of reasons. For example, higher than normal engine speed can add pressure tending to keep the gears engaged which requires additional effort to perform a gear shift from a position where the gears are thus engaged to the neutral position where the gears are, of course, disengaged. A binding linkage can also hinder a gear shift. Further, a new gearset can add to binding until the gears are broken in. Further yet, although any one of the aforementioned criteria may not create a binding gear shift alone, a combination of these factors may create additional undesired effort in shifting from a gear position to neutral.
It is therefore desirable to improve the linkage mechanism of the marine outboard engine to overcome the aforementioned problems.
The present invention relates to a shift linkage having a linkage bracket to transmit motion from a drive linkage to a driven linkage that solves the aforementioned problems in an outboard motor. The linkage bracket has a slot that operably engages with a guide to facilitate gearshift from forward or reverse to neutral position during operation of an outboard marine engine. The arrangement provides for a lost motion effect in which initial movement of the drive linkage is translated to substantially vertical motion of the guide in the linkage bracket to activate a switch, and then further movement of the drive linkage is then translated to the driven linkage. The result of the lost motion in the direction parallel with the drive and driven linkage provides free play to the linkage to reduce gearshift binding.
Accordingly, the present invention includes a shift linkage having a linkage bracket, a drive linkage and a driven linkage. The linkage bracket has an upper portion and a lower portion, wherein the lower portion is offset from the upper portion. The upper portion also has a pivot point and a tongue extending downwardly from the pivot point and in a common plane with the pivot point and the upper portion. The lower portion has a slot parallel to the tongue and leading to a lost motion channel in the lower end of the slot. An upper end of the lost motion channel is wider than the slot leading to the lost motion channel thereby forming a pair of guide stops in the offset lower portion of the linkage bracket to limit the amount of vertical movement. A guide is disposed in the slot and is configured to ride along the lost motion channel. The drive linkage is connected to the tongue and the driven linkage is connected to the guide to receive linear motion from the drive linkage after an initial movement is translated to create a lost motion that enhances the transfer of the motion through the shift linkage and thus reduce the binding effect.
In accordance with another aspect of the invention, a shift linkage is disclosed for use in an outboard motor having an engine coupled to a marine propulsion unit having forward and reverse operation. The outboard motor includes the aforementioned shift linkage, and further includes a switch positioned about the slot of the linkage bracket and connected to an ECU of the outboard motor. A driven linkage is coupled to the marine propulsion unit at one end and to the guide of the linkage bracket at another end. Initial movement of the drive linkage is translated to substantially vertical motion of the guide in the linkage bracket to activate the switch, after which, further movement of the drive linkage is then translated to the driven linkage.
In accordance with yet another aspect of the invention, a method of transmitting linear motion from a drive linkage to a driven linkage through a linkage bracket to ease shifting of an outboard motor is disclosed. The method includes the steps of applying a linear force to a drive linkage, and during a first phase of shifting, the linear force causes a lost motion in a direction parallel to the linear force and creating a motion in a transverse direction to the linear force through a linkage bracket. During a second phase of shifting, the linear force causes the linkage bracket to pivot and significantly move the driven linkage in the direction parallel to the linear force.
Various other features, objects and advantages of the present invention will be made apparent from the following detailed description and the drawings.